【作者】 何岩；

【导师】 刘寒冰；

【作者基本信息】 吉林大学 ， 道路与铁道工程， 2010， 博士

【摘要】 本文依托国家高科技研究发展计划项目(863计划)《季节冻土区路基抗冻融稳定控制技术研究》(2007AA11Z114)和国家自然科学基金项目《冻融循环后路基材料力学特性的静动参数转换理论及试验研究》(50978117),在季节性冰冻地区,针对聚丙烯纤维改良粉煤灰土这种路基填料,主要开展了以下几方面的研究工作:1.对聚丙烯纤维改良粉煤灰土的加固机理进行深入分析,通过无侧限抗压强度试验确定聚丙烯纤维的最佳掺入量,讨论不同纤维掺量对粉煤灰土强度的影响。研究聚丙烯纤维对粉煤灰土脆性破坏形式的影响,并对改良效果进行评价。2.在大量的室内动三轴试验基础上,研究纤维改良土在车辆动荷载作用下的动力特性。系统分析围压σ3、固结比K等对改良土动强度的影响,改良土动强度指标c_d、φ_d的变化规律,动应变水平与动模量之间的关系,并对纤维改良土、粉煤灰土,这两种土体的动强度与动模量进行对比分析。3.模拟季节性冰冻地区的气候条件,设计新试验。对改良土试样进行冻融循环试验,定量分析冻融循环作用对改良土动强度与动模量的影响。对一定压实系数、含水率、围压、加荷频率条件下的试样变形、冻融循环次数与动应力之间的关系进行研究。利用最小二乘法原理对冻融循环后的试验数据进行归一化处理,建立动强度随冻融循环次数变化的衰减模型、动模量随冻融循环次数变化的损失模型。4.通过冻融循环试验和室内UU(不固结不排水剪)静三轴试验,获得冻融循环作用下改良土的静强度指标c、φ值,对改良土的静强度特性进行定量分析。利用ABAQUS有限元分析软件对静三轴试验进行数值模拟,将试验值与模拟值对比分析,验证试验数据的准确性与可靠性,建立纤维改良土动、静力学参数之间的关系模型。参数模型的建立,在一定情况下,可以大大减少试验工作量,提高工作效率。更多还原

【Abstract】 China’s highway department said improved earth or stabilized soil for the solidified soil. Refers to soil admixture of lime, fly ash, cement and other inorganic materials or organic materials, thereby enhancing the performance of soil engineering. Improved soil and fly ash soil before compared to the performance of various aspects of the project there is a certain degree of enhancement and improvement. Mainly as follows: to improve the soil physical mechanical properties, increasing the internal friction angle ? and cohesion C, to improve soil shear strength, so that carrying capacity has been significantly improved; To improve the capacity of soil and water resistance to freeze-thaw stability, improve the durability of soil; to make the application of soil material to be expanded to sufficient raw materials. Because there are many advantages, improved soil technology in road works have been widely used to bring good social and economic benefits.Fly ash generated by coal-fired power plant, an industrial waste slag, with the proportion of small, high intensity, uniform gradation, permeability, good water stability and good engineering properties, can be used as embankment fill. Some countries in Europe and America in the 20th century, 70 years large-scale use of fly ash subgrade projects, our highway department in 80 years began to fly ash used for filling embankment. Reinforced fly ash can improve the soil while the engineering properties of subgrade soil, but can not effectively improve the roadbed soil cracking and compressive strength. Tends to brittle fracture, so that the road to form vertical and horizontal cracks, but also with anti-piping ability is poor, saturated by the vibration loads easily liquefied shortcomings. Therefore, the need for further improvement measures. In this paper, seasonal frozen regions of the subgrade soil was improved, in the amount of fly ash soil incorporation of polypropylene fibers. Through the unconfined compressive strength test, freeze-thaw cycle test and indoor static and dynamic triaxial tests, analysis of the polypropylene fiber modified fly-ash soil static and dynamic characteristics of mechanical parameters, using regression analysis on the parameters of the relation between fitted with a preliminary discussion, for a reasonable understanding of improved soil static and dynamic mechanical parameters of the relationship of some significance, and to improve soil in engineering and engineering design of rational use of theoretical basis, has important practical and theoretical significance. Through the analysis of test results obtained the following conclusions:（1）Join polypropylene fibers, the fibers in the fly ash within the soil to form a random network structure of space support system, constraints of displacement and deformation of soil particles, so that cracks have been delaying the development of an effective improvement in the form of its brittle failure. Polypropylene fiber can be greatly improved by adding fly ash soil unconfined compressive strength, when the fiber fraction of 1%, the strength values increased 74%, improving the best, the best ratio. In the engineering sense, polypropylene fiber modified fly-ash soil as subgrade filling, help to improve strength and stability of the roadbed.（2）The use of polypropylene fibers of fly ash improved soil, its dynamic strength was significantly greater than the dynamic strength of fly ash soil, and both the dynamic intensity with the increase in the number of load cycles decline, with the increase of confining pressure change Great. As the confining pressure increases the dynamic strength of improved soil magnitude greater than that of fly ash to improve soil. When the confining pressure, respectively 100KPa, 200KPa, 300KPa, the improvement of soil dynamic strength of fly ash soil were higher than 27.9%,31.1% and 26.1%. This indicates that at high confining pressure, fiber specimen greater impact on the dynamic strength.（3）Improved soil affected by the impact of dynamic strain smaller than that of fly ash soil, dynamic modulus E_d increases with the dynamic strainε_d diminishes. Action should be disguised at the same time, improved soil dynamic modulus is greater than about 20% fly-ash soil. Freeze-thaw cycles can lead to improved soil and fly ash to reduce the dynamic strength of soil, but the improved rate of decline in soil is less than the dynamic strength of fly ash soil. Improved soil after 6 freeze-thaw cycles, the dynamic strength remained stable, in the confining pressure for 200KPa and 300KPa, the dynamic strength of a reduction of about 20%, with a good frost durability, cold areas during the quarter is more satisfactory the roadbed material.（4）Least-squares method using freeze-thaw cycle test data after the fitting has been dynamic changes in strength with attenuation of freeze-thaw cycles modelsτ_d =Ae^Bn and dynamic modulus of freeze-thaw cycles change polynomial model. Polypropylene fiber modified fly-ash soil undergoing a freeze-thaw cycles, the dynamic modulus decreased, the second freeze-thaw, the dynamic modulus is higher than the first time. 6 times freeze-thaw cycles, the dynamic modulus stabilized, the average move modulus is greater than the initial move of the volatility of the modulus fluctuations, freeze-thaw cycles the loss of a small dynamic modulus.（5）Freeze-thaw cycles on the dynamic modulus than for static modulus of high-impact, when the static and dynamic model for money within a certain range, it has the function to determine the relationship between the test conditions do not have the circumstances, if known to move , static modulus one, then the functional relationship can roughly estimate the value of another modulus.（6）Freeze-thaw cycles on the dynamic and static triaxial tests the value of C has great similarities. When the C value and the C_d value of stable value when stabilized with non-freeze-thaw ago, are down about 8%. Show improved resistance to freezing and thawing soil with good performance. C value and the C_d value of fitting the curve after the effects of good, the correlation coefficient R² =0.89. The first three freeze-thaw cycles on theφ_d value and theφvalue of a great influence on the future of their three little effect. Stable value of stability when compared with non-freeze-thaw before both fell by around 11%. Theφ_d and theφafter the relationship with the fitting curve is quadratic curve, correlation coefficient R² = 0.98, with a strong correlation.（7）UU triaxial tests obtained by the intensity of the comparison with simulated values and found good agreement between the two, between the error rate less than 10%, indicating a static triaxial test data and reliable sex. It also shows the use of finite element analysis software to simulate a certain extent, can replace part of the test, so that large amount of test cases, can reduce some of the workload and improve work efficiency.更多还原